Hi,

I am completely new to the world of programming and have been following Pauls SwiftUI course. I have managed to complete the first challenge and create a temperature unit conversion app.

The code isn't very pretty and there are lots of if else in order to convert but it seems to work fine.

I have run in to a problem though which I am wondering if there is a solution.

Currently the output text box will display the calculation before the input value is entered. For example:

If Celcius is selected as input and Kelvin as output, 273.15 is displayed if there is no input value.

Is there a way to stop this? Please see the code below.

 @State private var inputUnit = 0
    @State private var outputUnit = 0
    @State private var inputNumber = ""

    let unit = ["Celcius", "Farenheit", "Kelvin"]

    var conversion: Double {

        var conversionResult: Double = 0
        let inputDouble = Double(inputNumber) ?? 0

           // Convert C
        if inputUnit == 0 && outputUnit == 1 {
                 conversionResult = inputDouble * 1.8 + 32
        } else { if inputUnit == 0 && outputUnit == 2 {
                conversionResult = inputDouble + 273.15
        } else { if inputUnit == 0 && outputUnit == 0 {
                 conversionResult = inputDouble
            // Convert F
        } else { if inputUnit == 1 && outputUnit == 0 {
            conversionResult = (inputDouble - 32) / 1.8
        } else { if inputUnit == 1 && outputUnit == 1 {
                 conversionResult = inputDouble
        } else { if inputUnit == 1 && outputUnit == 2 {
            conversionResult = (inputDouble - 32) * 5 / 9 + 273.15
            // Convert K
        } else { if inputUnit == 2 && outputUnit == 0 {
            conversionResult = inputDouble - 273.15
        } else { if inputUnit == 2 && outputUnit == 1 {
            conversionResult = (inputDouble - 273.15) * 9 / 5 + 32
        } else { if inputUnit == 2 && outputUnit == 2 {
            conversionResult = inputDouble
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
        return conversionResult
    }

Section(header: Text("Converted Value")) {
                Text("\(conversion, specifier: "%.2f")")

Any help is much appreciated!

The reason why it shows the calculated output amount is that your inputDouble is default to 0. If you put a guard let then until a number is type then output will show0

eg

var conversion: Double {
    guard let inputDouble = Double(inputNumber) else {
        return 0
    }

    var conversionResult: Double = 0
    // Convert C
    if inputUnit == 0 && outputUnit == 1 {
        conversionResult = inputDouble * 1.8 + 32
    } else if inputUnit == 0 && outputUnit == 2 {
        conversionResult = inputDouble + 273.15
    } else if inputUnit == 0 && outputUnit == 0 {
        conversionResult = inputDouble
        // Convert F
    } else if inputUnit == 1 && outputUnit == 0 {
        conversionResult = (inputDouble - 32) / 1.8
    } else if inputUnit == 1 && outputUnit == 1 {
        conversionResult = inputDouble
    } else if inputUnit == 1 && outputUnit == 2 {
        conversionResult = (inputDouble - 32) * 5 / 9 + 273.15
        // Convert K
    } else if inputUnit == 2 && outputUnit == 0 {
        conversionResult = inputDouble - 273.15
    } else if inputUnit == 2 && outputUnit == 1 {
        conversionResult = (inputDouble - 273.15) * 9 / 5 + 32
    } else if inputUnit == 2 && outputUnit == 2 {
        conversionResult = inputDouble
    }

    return conversionResult
}

PS when else if not else { if

That's awesome Nigel. And thank you for posting a more elegant solution than my messy code! Still so much to learn.

Craig

Craig. I was impressed with your logic (as you are only on Day 19) but when you come to use alot of if statements then you can look at switch statements. I just put it in so you can see there is different ways to code (there more then one way to skin a c..ode)

Just a couple of pointers on your code. Look at name of variable etc and try to make them "read" natural (this is hard sometimes) rather then putting Double, ( i know you will see things like numberString for a number that is a String but if the variable is a number(Double, Int etc) then just put a name.

When you put comments give details. eg

// Convert to Kelvin from Celsius

Keep up the good work and happy coding